Treatment of a workpiece with granular media, such as in abrasive blast cleaning and in shot peening, has become relatively common. The flow rate of the granular media in these applications is often set by a fixed orifice or sometimes by a mechanical or electrical valve; however, the actual flow rate is not commonly sensed. The flow rate through the flow path may vary during operation, so it is desirable to have a flow sensor measuring the actual flow rate, which can be processed and displayed to assist in effective control of the process.
Many flow sensors for such applications have been proposed, often using the reaction force of the impact of a falling stream of media onto a slanted surface. However, such flow sensors wear quickly because of the abrasive nature of the impact of the falling media. These devices often have hinges or bearings subject to contamination which affects accuracy and performance. Flow sensing devices incorporating, for example, strain gauges, bearings, or hinges require difficult and delicate procedures for maintenance. Often, delicate wiring connected to the flow sensor is broken or damaged during such maintenance procedures.